Sorry, I was thinking the car were final assembled at PAS including the motor since they built them, but here's the write up from 89tta.turbobuicks:
"Originally conceived by Bill Owen of Pontiac, the 20th Anniversary Turbo Trans Am project was outsourced to PAS, Inc., an engineering firm led by Jeff Beitzel. Beitzel and his team did most of the TTA development work. The V6 turbo engines were built by PAS at their 40,000 square foot City of Industry, CA plant. From there, they went to GM's plant in Van Nuys, CA to be installed into GTAs on the F-Body assembly line. The cars were then shipped back to PAS for final assembly, testing, and quality control. Incidentally, the GTA chassis were selected at random, thus there is no correlation between VIN number and production sequence number. The actual number of cars to be produced had ranged from 500 to 2,500 until GM finally settled on 1,500. In all, a total of 1,555 Turbo TAs were manufactured."